Liquid hydrocarbon fuel compositions



itd States This invention relates to liquid hydrocarbon distillate fuels that are capable of reducing formation of solid deposits under storage or service conditions, and more particularly, to liquid hydrocarbon fuel distillates that contain small amounts of oil-soluble copolymers of higher alkyl esters of acrylic or methacrylic acid and long-chain, N-substituted quaternary ammonium salts of acrylic or methacrylic acid.

Deposit formation has been found to occur during normal use and/or storage of a wide variety of liquid hydrocarbon distillate fuels. These deposits are objectionable as they interfere with proper functioning of the hydrocarbon distillates as fuels. For example, gasoline motor fuels, especially auto-motive motor fuels, have been found to form deposits in the induction systems of engines in which they are employed as fuels. For example, carburetor deposits, which cause rough idling and stalling, have been found troublesome. Such deposits have been attributed in part to the introduction into the carburetor of engine blowby products, that is, partial combustion products of gasoline that pass from the engine combustion chambers into the crankcase and then into the carburetor by way of the oil-breather tube. These blowby products condense and deposit in the carburetor throat where they entrap dust, gum, and other deposits. Accumulated deposits of this kind interfere with proper engine functioning.

Combustion gas turbine fuels, particularly aviation turbine fuels, that is, jet fuels, also have been found to form deposits during use, which deposits tend to clog the fuel nozzles or orifices by way of which the fuel is introduced iutothe combustion chambers of engines in which the fuel is being consumed. The formation of these deposits is attributed to the use of fuel as a cooling medium to remove heat from lubricating oil that has absorbed heat developed by the compression of combustion air, fuel combustion, and friction. In such use the fuel is subjected to service temperatures of the order of 300 to 400 F. for substantial periods of time, and to even higher temperatures, of the order of 500 F. or more for shorter periods of time, in the area of the fuel nozzles or orifices. Under such temperature conditions, the less stable components of the fuel tend to undergo degradation as a result of polymerization, oxidation, and thermal decomposition reactions and to form solid or semisolid deposits that interfere with proper functioning of jet engines.

By way of still further example, ordinary furnace oils containing cracked components, particularly those containing a mixture of catalytically cracked and straigl1trun fuel oil distillates, also tend to form deposits during storage that interfere with proper combustion of the oil. These deposits have been attributed to the polymerization of the olefinic and olefinic-aromatic components of the oil.

The present invention relates to stable petroleum distillate fuels that reduce deposit formation and that are thereby more suitable for use as fuels. We have found that deposit formation in the presence of petroleum distillate fuels can be reduced by incorporating therein a small amount of a copolymer of (a) a monomeric alkyl ester of acrylic or methacrylic acid whose alkyl substituent contains 8 to 18 and preferably 12 to 18 carbon atoms, and (b) a monomeric quaternary am- 3,020,135 Patented Feb. 6, 1962 monium salt of acrylic acid or methacrylic acid, one of whose four covalent Nbonds is attached to a monovalent aliphatic hydrocarbon radical containing 8 to 18 and preferably 12 to 18 carbon atoms, two other of whose covalent N-bonds are attached to monovalent aliphatic hydrocarbon radicals containing 1 to 18 carbon atoms, or aralkyl radicals containing 7 to 23 carbon atoms, and whose remaining covalent N-bond is attached to an alkyl group containing 1 to 4 carbon atoms. The quaternary ammonium salt monomers that form the copolymers disclosed herein are preferably copolymerized with the ester monomers in ratios of about 005' to 0.75:1 by weight, but other ratios can be used. For example, ratios in the range of 0.03:1 to 1:1 canv be used. Polymers prepared from the above-indicated monomer ratios will usually be characterized by a nitrogen content in the range of about 0.04 to 3 percent by weight, We normally prefer to employ copolyrners containing at least about 0.2 percent and preferably about 0.2 to 2 per-cent nitrogen but copolymers having greater and lesser nitrogen content can be used. Specific examples of copolyrners with which excellent results can be obtained are the 1:9 weight ratio copolymers of monomeric distearyldiamethyl-ammonium methacrylate and monomeric lauryl methacrylate, monomeric mixed octadecenyland octadecadienyltri-rnethylammonium methacrylate and monomeric lauryl methacrylate, and monomeric tri(rnixed caprylyl-decyl)-methylamrnoniurn methacrylate. Examples of other copolyrners whose use is included by the invention are the 0.05:1, the 01:1, the 05:1, and the 1:1 weight ratio copolymers of monomeric dioctadecenyldimethylammonium, octadecenyldimethylethylammonium, octadecenyltrimethyl-ammonium, lauryltrimethylammonium, distearyldimethyl-ammonium, dilauryldimethylammonium, dihexadecyldimethyl-ammonium, hexadecyltrimethylammonium, octadecyltrimethyl-ammonium, laurylbenzyldimethylammonium, lamyldimethyl- (ethylbenzyl)ammonium, and lauryldimethyl(methylbenzyl)-ammonium acrylates and methacrylates, and monomeric n-octyl, lauryl, Oxo-octyl, 2-ethylhexyl, Oxotridecyl, and n-hexadecyl acrylates and methacrylates. We prefer to employ the copolymers in hydrocarbon distillate fuels in proportions of about 10 to 50 pounds of copolymer per 1,000 barrels of distillate fuel, but other proportions can be used. For example, the co-, polymers can be employed in amounts of as little as five pounds per thousand barrels of fuel or of up to 0.1 percent by weight of the fuel, that is, about 300 pounds per thousand barrels of distillate fuel.

The exact manner in which the copolymers disclosed herein function to reduce deposit formation is not definitely known. Inasmuch as the copolymers can remove preformed deposits, it is considered that the copolymers function at least in part by preventing formation of solid particles of a size sufficient to interfere with proper functioning of the hydrocarbon liquids as fuels. However, the copolymers may also function in part by undergoing sacrificial degradation or by interaction with the deposit precursors, that is, the more unstable fuel components that tend to form solid deposits, whereby formation of deposits by the depositprecursors is delayedor prevented. The latter mechanism might be suggested bythe fact that some hydrocarbon distillate fuels containing the copolymers, when subjected to an accelerated stability test, have been found to possess a darker color than the uninhibited fuel, notwithstanding the fact that the darker, inhibited fuels are substantially less subject to deposit formation than the uninhibited fuels.

The copolymers disclosed herein are preferably prepared by the method disclosed in our copending application Serial No. 862,056, filed December 28, 1959. Briefly,

such method involves reacting the desired monomers in v weight ratios of about 0.03 'to 1 part by weight of the erably a solvent, such as toluene, benzene, ethyl acetate or other solvents having similar chain transfer activity, at a temperature in the range of 75 C. to 150 C., preferably 25 C. to 150 C., in the presence of a few hundredths percent to two percent, preferably 0.2 to 1.0 percent, of a free-radical catalyst such as benzoyl peroxide, lauroyl peroxide, or alpha,alpha'-azodiisobutyronitrile, preferably in the substantial absence of oxygen, until the rate of formation of larger polymer molecules has declined substantially, usually after about 3 to 35 hours, as determined by periodic sampling of the reaction mixture and observing the viscosity thereof.

The preferred ester monomers from which the copolymers disclosed herein are prepared can be represented by the general formula: CH =CRCOOR where R is hydrogen or a methyl radical, and R is a straightor branchedchain alkyl group containing 12 to 18 carbon atoms, such as lauryl, Oxo-tridecyl, n-hexadecyl, or n-octadecyl.

'Illepreferred quaternary ammonium salt monomers from which the herein described copolymers are prepared can be represented by the general formula:

CFC RC ON where R is as defined above R is an alkyl, alkenyl, or

alkadienyl radical containing 12 to 18 carbon atoms, such as lauryl, myristyl, n-hexadecyl, n-octadecyl, n-octadecenyl, or n-octadecadienyl, and R and R are radicals of the same kind as R, or alkyl radicals containing 1 to 4 carbon atoms such as methyl, ethyl, propyl, or butyl, or a mononuclear aralkyl radical containing 7 to 23 carbon atoms, such as benzyl, tolylethyl, or a polypropylated aralkyl radical such as p-tetraisopropylbenzyl, and R"" is an alkyl radical containing 1 to 4 carbon atoms. Neither the alkyl ester substituents of the ester monomers nor the long-chain groups attached to the covalent N-bonds of the quaternary ammonium monomers need be pure; instead these substituents can comprise mixtures of radicals derived from commercially available materials. For example, the alkyl ester substituents of the ester monomers can be derived from a mixture of synthetically produced, isomeric, branched-chain alcohols such as is produced by the well-known Oxo-synthe'sis process. Alternatively, the ester substituents can be derived from a mixture of fatty alcohols obtained from coconut oil fatty acids or tallow fatty acids or other acids derived from naturally occurring fats or oils. Similarly, the long-chain groups attached to the covalent N-bonds of the nitrogenous monomer can comprise a mixture of alkyl, alkenyl, and/or alkadienyl groups derived from commercial materials such as coconut oil fatty acids, soya fatty acids, or tallow fatty acids. When the substituents referred to above are derived from natural fats and oils, the mixed radicals will comprise homologous mixtures of alkyl, or alkyl and alkenyl, or alkyl, alkenyl, and alkadienyl radicals containing an even number of carbon atoms from 8 to 18. The ester substituents of the ester monomer and the N-substituents attached to the covalent N-bonds of the nitrogenous monomer can also be substituted, if desired, with nonhydrocarbon substituents such as halogens, hydroxyl, sulfhydryl, carbonyl, or the like that do not adversely affect the oil-solubility or depositinhibiting characteristics of the salts. I The preferred copolymers of this invention are-copolymers of the above-indicated preferred monomers in weight ratios in the, range of about 0.05 to 0.75 part by weight of quaternary ammonium salt monomer to 1 part by weight est r JO HJ LT- The average molecular weight of the copolymers disclosed herein will normally be greater than about 2,000, and is preferably greater than about 7,500, as determined by conventional methods. Usually, the molecular weights of the copolymers will not exceed about $00,000, but the molecular weights can be greater. In fact copolymers having molecular weights of any upper limit can be used, provided that the molecular weight is not so great as to to render the copolymers insoluble in the liquid hydrocarbon fuel distillates.

It is important for the purposes of this invention that the copolymers be prepared directly from the monomers rather than by indirect methods, as the copolymers obtained by direct copolymerization of monomers are chemically and functionally distinct and different from copolymers prepared by indirect methods, at least partly by reason of their more uniform and more controlled composition.

The copolymers disclosed herein can be employed in a wide variety of normally liquid hydrocarbon fuel distil lates. For example, they can be employed in motor gasoline of both premium and regular grades, aviation gasoline, furnace oils, such as those used in ordinary domestic heating installations, of which No. 1 and No. 2 fuel oils are examples, light and medium diesel fuel, aviation turbine fuel, and the like. Motor gasolines, aviation gasolines, distillate fuel oils and diesel fuels are defined in the ASTM Standards on Petroleum Products and Lubricants under the respective specifications ASTM D439, D-910, D496, and 13-975. Aviation turbine fuels of the type included by the present invention are liquid hydrocarbon mixtures of the kind defined by the following specifications: MILJ-5 16E (Referee JP-4 Fuel), MIL-J- 5624D (JP-4, JP-S Fuel), MIL-F-25656 (JP-6 Fuel), MIL-F-25524A, MIL-F-25558B (RI-1 Fuel), MIL-F- 25 5 76A (RP-1 Fuel), and American Airlines Specification No. M6-4A.

The copolymers disclosed herein are useful when employed in liquid hydrocarbon fuel distillates in amounts sufficient to reduce the deposit-forming tendencies of the oils. The copolymers disclosed herein are not necessarily exactly equivalent in effectiveness, and all of the distillate fuels are not necessarily equivalently responsive thereto; therefore, the optimum proportions of copolymer may vary somewhat in accordance with these factors. Usually, some improvement will be obtained by the use of as little as about five pounds of copolymer per thousand barrels of fuel and a major improvement will be obtained by the use of 10 to 25 pounds per thousand barrels. Usually, we prefer to employ the copolymers in proportions not exceeding about 50 pounds per thousand barrels but insome instances it may be desired to employ the copolymers in proportions as great as 300 pounds per thousand barrels. Normally, no additional advantage will be obtained from the standpoint of inhibiting deposit formation by the use of greater proportions.

The herein described copolymers can be incorporated in the hydrocarbon fuel distillates in any convenient way. For example, they can be added directly to the fuels either as such or in the form of concentrated solutions in solvents such as toluene, kerosene, or light lubricating oil in order to facilitate blending. If desired, the copolymers can be added to the fuels in conjunction with other compatible addition agents that are capable of improving one or more properties of the fuels. In instances of blended fuels, the copolymers can be added to one of the fuel components prior to blending. Some stirring of the fuel during admixture with the copolymers, with or without moderate heat, may be desirable to facilitate rapid formation of a homogeneous mixture, but stirring is not absolutely necessary.

The effectiveness of the herein disclosed copolymers to inhibit deposition of solids from distillate fuels has been demonstrated in several different ways. Thus, according to one method employed, separate samples of; an aviation,

turbine fuel containing representative copolymers of the class disclosed herein were subjected to the CFR Fuel Coker Test procedure described in ASTM Standards on Petroleum Products and Lubricants for 1959, ASTM D1660-59T. In accordance with this test method, aviation turbine fuels are subjected to flow conditions and temperature stresses similar to those in jet aircraft engines. The test apparatus comprises a fuel system containing two heated sections: 1) a preheater section that simulates the hot fuel line sections of a jet engine as typified by an engine fuel-lubricating oil cooler and (2) a filter section that simulates the nozzle, or fuel inlet area of the combustion zone of an aircraft jet engine where fuel degradation products may be trapped. A precision sintered, stainless stell filter is employed in the filter section to trap fuel degradation particles formed during the test. The extent of the build-up of fuel degradation particles in the filter sections is indicated by the pressure differential across the test filter and this is used as an index of the high temperature stability of the aviation turbine fuel. In carrying out the test, the temperature of the fuel at the outlet of the preheater section was maintained at 410 F. and the filter section was maintained at 500 F. During the test, the fuel was caused to flow through the test apparatus at the rate of six pounds per hour and the duration of the test was five hours.

Two test fuels, hereinafter referred to as aviation turbine fuel A and aviation turbine fuel B, were employed in Three dilferent copolymers, hereinafter referred to, respectively, as copolymers 1, 2, and 3, were employed in the test. Copolymer 1 was a 1:9 weight ratio copolymer of di(hydrogenated talloW-alkyl) dimethylammonium methacrylate monomer, principally distearyldimethylarnmonium methacrylate monomer, and lauryl methacrylate monomer as a 33 /3 percent by weight solution in a light lubricating oil. This material was prepared by reacting 33.6 grams of di(hydrogenated tallow-alkyl)diinethylammonium methacrylate monomer with 302.4 grams of lauryl methacrylate monomer in the presence of 2.02 grams of a catalyst consisting of alpha,alpha'-azodiisobutyronitrile, in 282 grams of a solvent (toluene) for the reaction mixture, at a temperature of 67 to 73 C., for about 6% hours, with stirring, and with nitrogen gas being bubbled through the reaction mixture throughout the reaction period. A portion of the reaction product having the solvent removed had the following properties:

Intrinsic viscosity, at 77 F. in toluene;

As determined by shear method of F. Bueche and S. W. Harding, Journal of Polymer Science, vol. XXXII, pages 177-186 (1958), with application of appropriate instrument calibration constant.

To the balance of the toluene solutionof the copolymer was added 556 grams of a light lubricating oil, and toluene 6 was removed under heat and reduced pressure, to produce the lubricating oil solution referred to above.

Copolymer 2 was a 1:9 weight ratio copolymer of a mixed octadecenyland octadecadienyl-(i.e., soya-alkyl)trimethylammonium methacrylate monomer and lauryl methacrylate monomer as a 33 /3 percent by weight solution in a light lubricating oil. This material was prepared by reacting 40.9 grams of soya"-alkyltrimethylammoniurn methacrylate and 360.0 grams of lauryl methacrylate in the presence of 2.0 grams of alpha,alpha'- azodiisobutyronitrile in 200 grams of toluene as a solvent for the reaction mixture. The reaction mixture was stirred and heated at 63 to 70 C. for 5% hours, nitrogen being bubbled through the mixture during the entire period. The viscous toluene solution of the copolymer was dissolved in 803.0 grams of an SAE 10W lubricating oil and the toluene was removed under reduced pressure with heating. The resulting copolymer concentrate had a nitrogen content of 0.11, and the copolymer itself had an intrinsic viscosity in toluene at 77 F. of 0.25 deciliter per gram- Copolymer 3 was a 1:9 weight ratio copolymer of tri- (mixed caprylyland decyl)methylammonium methacrylate and lauryl methacrylate as a 33 /3 percent by weight solution in a light lubricating oil. This material was prepared by reacting 25.0 grarns of tri(caprylyl-decyl)methylammonium methacrylate monomer with 225.0 grams of lauryl methacrylate monomer in the presence of 1.5 grams of alpha-alpha-azodiiso-butyrontrile, all in an SAE 10W lubricating oil solvent, with stirring and heating at 74 to 79 C. for 6% hours, nitrogen being bubbled through the mixture during the entire period. The resulting copolymer concentrate had a nitrogen content of 0.14 percent by weight.

The results of the foregoing tests were as set forth in the following table:

Table A Sample Make-Up, Volume percent:

Aviation Test Fuel A 100 100 Aviation Test Fuel B 100 100 Addition Agent, Active Ma.-

terial Added, 20 Lbs/1,000 Bb1s.--

Oopolyrner 1 20 Copolymer 2. 20 Copolymer 3. 20 Deposits Test:

Time to Reach a lressure Drop pf 10 111. Hg, M111 60 191 300 295 300 Time to Reach a Pressure Drop of 25 in. H Min 76 240 300 300 300 Pressure Drop at300 Mim, In. Hg. 25 25 1. 4 10. 3 5.0

The results set forth in the preceding table demonstrate the marked reduction in the deposit-forming tendencies of jet fuels imparted by the copolymers disclosed herein.

An example of a fuel containing a copolymer one of whose covalent N-bonds is attached to an aralkyl radical is aviation test fuel A containing 20 pounds active material per thousand barrels of a 33 /3 percent solution in light lubricating oil of a 1:9 weight ratio copolymer of mixed C chiefly C alkylbenzyldimethylammonium acrylate monomer, that is, "coco-alkylbenzyldirnethylammonium acrylate monomer, and lauryl acrylate monomer. This copolymer concentrate is prepared by reacting 25 grams of the quaternary ammonium salt monomer with 225.0 grams of lauryl acrylate monomer dissolved in grams of toluene and in the presence of 1.5 grams of alpha,alpha'-azodiisobutyronitrile, at 65 -70 C. for six hours, nitrogen being bubbled through the mixture throughout the reaction period. The toluene solution of the resulting copolymer is dissolved in 500.0 grams of a light lubricating oil and toluene is removed by a combination of heat and reduced pressure.

The ability of the copolymers disclosed herein to inhibit induction system deposits was demonstrated by subjecting separate gasoline samples containing copolymers l, 2,

and '3, respectively, in the proportion of 50 pounds of copolymer (active material) per 1,000 barrels of fuel, to an induction system deposits test. This test was carried out by first passing one liter of light fluid catalytically cracked gasoline containing 20 of a solution of a preformed gasoline gum through a steam-jacketed U-tube along with air in a ratio of 5.5 volumes of air to 1 volume of fuel to form a deposit. The same amount of a test fuel containing the desired copolymer was then passed through the system along with air in the same ratio as previously described. The weights of deposits remaining in the U-tube after use of only the uninhibited test fuel, and with the experimental copolymer-containing test fuel were determined after first washing the U-tube with a number of batches of V.M. and P naphtha until no discoloration of the last portion was evident, by then dissolving the remaining deposits in acetone, evaporating the acetone, and weighing the residue. The test fuel in this instance was a gasoline having an API gravity of 582, an olefin content of 26 percent, an aromatics content of 25.5 percent, a tetraethyl lead content of 2.94 ml./gal., an antiknock rating of 86.8 by the Motor Method and of 98.0 by the Research Method, a 50 percent ASTM distillation point of 228 F., and a 90 percent ASTM distillation point of 315 F. The results of the tests are presented in the following table:

Table B Wt. of adhering deposits, mg. Control 58.5 Base fuel plus copolymer 1 35.8 Base fuel plus copolymer 2 32.5 Base fuel plus copolymer 3 44.1

As will be seen from the foregoing results, the copolymers described herein are capable of effecting a marked reduction in induction system deposits.

It has incidentally been found that gasolines that normally tend to promote engine stalling by carburetor icing, that is, have a 50 percent ASTM distillation point not greater than about 235 F., particularly 200 F. or less and that contain the copolymers described herein in deposit-inhibiting proportions, also exhibit reduced engine stalling tendencies. The stall-reducing properties of the copolymers were demonstrated by introducing test fuel at about 50 F. together with air at ambient temperatures, that is, 70 to 80 F, and about 90 percent relative humidity at controlled rates to a glass vaporizer chamber held at an absolute pressure of 6 inches of mercury, and by observing the time for icing to occur on a brass tube positioned in the vaporizer chamber. Performance of the test fuel was determined by comparing the time for ice formation on the brass tube with that required for the uninhibited fuel under the same test conditions. Test results are expressed in terms of the isopropanol equivalent concentration required in the uninhibited fuel to obtain the same antiicing action. The fuel employed in the test was a gasoline having a 50 percent ASTM distilla tion point of 200 F. The results of this test were as follows:

The deposit-inhibiting properties of the copolymers described herein in furnace oil were demonstrated by subjecting a test oil containing copolymer 2 in the proportion of 20 pounds active material per 1,000 barrels of fuel to an accelerated storage stability test. In accordance with this test, 600 gram samples of an experimental fuel. oil were heated for 16, 40, and 6 4.hours at 210 F. in 21 1008 1y stoppered, clear glass bottle. Following the heating period, the samples were cooled to room temperature and filtered by suction through tared, medium porosity, fritted glass, Gooch crucibles. The sludge in the crucibles was washed with heptane. Complete removal of the sludge adhering to the inside of the sample bottles was accomplished by means of a rubber policeman and heptane. The crucibles were dried in an oven at 210 F. for one hour, cooled in a desiccator and reweighed. The increase in Weight was recorded as mg. sludge per 600 grams of oil. The test oil was a 35/65 by volume. blend of straight run and oatalytically cracked No. 2 fuel oil distillates. The results of the test were as follows:

Table D Control Inspections Control Copolymer 2 Color. Initial (ASTM D1500 58T) LLO LLO Stability Test:

Poten tial Insolubles at 16 Hours 20.0 0. 8 10 Hours 47. 8 0. 5 64 Hours. 55.1 3. 5 Color at- 16 Hours 3.0 L3. 5 40 Hours Li. 5 L7. 0 G4 Hours 5.0 L8. 0

From the results presented in the foregoing table it will be seen that the copolymers disclosed herein are capable of efiecting a marked improvement in the sludge-depositing tendencies of distillate fuel oils that are normally unstable during storage.

The specific embodiments set forth above are illustrative only, and similar results can be obtained by substitution in the fuel compositions of the preceding embodiments of equivalent proportions of other copolymers of the class disclosed herein. For example, there can be substituted with goodresults the 0.05:1, the 01:1, the 0.5 1, and the 1:1 weight ratio copolymers of (a) a monomeric dioctadecenyldimethylammonium, lauryltrirnethylammonium, distearyldimethylammonium, dilauryldimetha ylammonium, dihexadecyldimethylarnmonium, laurylbenzyldimethylammonium, lauryldimethyl(ethylbenzyl) ammonium, lauryl (methylbenzyl) dimethylammonium,

hexadecyltrirnethylammonium, and tristearylrnethylammonium acrylates or methacrylates and (b) monomeric n-octyl, lauryl, Oxo-octyl, 2-ethylhexyl, Oxo-tridecyl and n-hexadecyl acrylates or methacrylates.

It will be understood that other addition agents adapted to improve one or more properties of fuels can be incorporated in the compounded fuel compositions of this in-. vention. For example, there can be added antiknock agents, lead scavengers, antipreignition agents, antioxidants, corrosion inhibitors, cetane number improvement agents, combustion improvers, ignition promoters, and the like.

Numerous modifications and variations of the invention as herein set forth can be resorted to without departing from the spirit or scope of the invention. Accordingly, only such limitations should be imposed as are indicated in the claims appended hereto.

We claim:

l. A fuel composition comprising a major amount of a liquid hydrocarbon fuel distillate and a small amount, sufiicient to reduce deposit formation, of an oil-soluble copolymer of (a) a monomeric alkyl ester of an acid selected from the group consisting of acrylic and methacrylic acids, and whose alkyl ester substitutent contains 8 to 18 carbon atoms, and (b) a monomeric quaternary ammonium salt of an acid selected from the aforesaid group, one of whose covalent N-bonds is attached to a monovalent aliphatic hydrocarbon radical containing 8 to 18 carbon atoms, two other of whose covalent N-bonds are attached to members selected from the group. consisting of monovalent aliphatic hydrocarbon, radicalscon- 9 taining 1 to 18 carbon atoms, and aralkyl radicals containing 7 to 23 carbon atoms, and whose remaining covalent N-bond is attached to an alkyl radical containing 1 to 4 carbon atoms, said monomeric quaternary ammonium salt and said monomeric alkyl ester being copolymerized in a weight ratio in the range of about 0.03:1 to 1:1.

2. The fuel composition of claim 1 where the nitrogen content of the ccpolymer is in the range of about 0.04 to 3 percent by weight of the copolymer.

3. The fuel composition of claim 1 where the nitrogen content of the copolymer is in the range of about 0.2 to 2 percent by weight of the copolymer.

4. The fuel composition of claim 1 where said copolymer is present in the amount of about 5 to 300 pounds per 1,000 barrels of said distillate.

5. The fuel composition of claim 1 where said copolymer is present in the amount of about 10 to 50 pounds per 1,000 barrels of said distillate.

6. The fuel composition of claim 1 where two of the covalent N-bonds are attached to monovalent aliphatic hydrocarbon radicals containing 12 to 18 carbon atoms, and the remaining covalent N-bonds are attached to alkyl radicals containing 1 to 4 carbon atoms.

7. The fuel composition of claim 1 where two of the covalent N-bonds are attached to monovalent aliphatic hydrocarbon radicals derived from tallow fatty acids and the remaining two covalent N-bonds are attached to methyl groups.

8. The fuel composition of claim 1 where one of the covalent N-bonds is attached to a monovalent aliphatic hydrocarbon radical containing 12 to 18 carbon atoms, and the remaining covalent N-bonds are attached to alkyl radicals containing 1 to 4 cmbon atoms.

9. The fuel composition of claim 1 where one of the covalent N-bonds is attached to a monovalent aliphatic hydrocarbon radical derived from soya fatty acids, and the remaining covalent N-bonds are attached to methyl groups.

10. The fuel composition of claim 1 Where three of the covalent N-bonds are attached to monovalent aliphatic hydrocarbon radicals containing 8 to 18 carbon atoms, and the remaining covalent N-bond is attached to an alkyl group containing 1 to 4 carbon atoms.

11. The fuel composition of claim 1 where three of the covalent N-bonds are attached to caprylyl and decyl radicals and the remaining covalent N-bond is attached to a methyl radical.

References Cited in the file of this patent UNITED STATES PATENTS 2,616,922 Ringwald et a1 Nov. 4, 1952 2,617,781 Lytton Nov. 11, 1952 2,652,322 Hedrick et al Sept. 15, 1953 2,800,401 Lusebrink et a1. July 23, 1957 2,892,690 Lowe et al. Tune 30, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,020, 135 February 6, 1962 Elizabeth L. Fareri et a1.

It is hereby certified that error appears in the above numbered pat ent requiring correction and that the said Letters Patent should read as corrected below.

' Column 3, the formula should appear as shown below instead of as in the patent:

I ll/ CH -CRCOON\IF Signed and sealed this 19th day of June 1962.

SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

1. A FUEL COMPOSITION COMPRISING A MAJOR AMOUNT OF A LIQUID HYDROCARBON FUEL DISTILLATE AND A SMALL AMOUNT, SUFFICIENT TO REDUCE DEPOSIT FORMATION, OF AN OIL-SOLUBLE COPOLYMER OF (A) A MONOMERIC ALKYL ESTER OF AN ACID SELECTED FROM THE GROUP CONSISTING OF ACRYLIC AND METHACRYLIC ACIDS, AND WHOSE ALKYL ESTER SUBSTITUTENT CONTAINS 8 TO 18 CARBON ATOMS, AND (B) A MONOERIC QUATERNARY AMMONIUM SALT OF AN ACID SELECTED FROM THE AFORESAID GROUP, ONE OF WHOSE COVALENT N-BONDS IS ATTACHED TO A MONOVALENT ALIPHATIC HYDROCARBON RADICAL CONTAINING 8 TO 18 CARBON ATOMS, TWO OTHER OF WHOSE COVALENT N-BONDS ARE ATTACHED TO MEMBERS SELECTED FROM THE CONSISTING OF MONOVALENT ALIPHATIC HYDROCARBON RADICALS CONTAINING 1 TO 18 CARBON ATOMS, AND ARALKYL RADICALS CONTAINING 7 TO 23 CARBON ATOMS, AND WHOSE REMAINING COVALENT N-BOND IS ATTACHED TO AN ALKYL RADICAL CONTAINING 1 TO 4 CARBON ATOMS, SAID MONONERIC QUATERNARY AMMONIUM SALT AND SAID MONOMERIC ALKYL ESTER BEING COPOLYMERIZED IN A WEIGHT RATIO IN THE RANGE OF ABOUT 0.03:1 TO 1:1. 